英文科技文献阅读

阅读科技文献英文作文1. What is your opinion on the impact of technology on society?Technology has had a profound impact on society in recent years. On one hand, it has brought about significant improvements in healthcare, education, and communication. On the other hand, it has also led to job displacement, social isolation, and privacy concerns. While technology has undoubtedly made our lives easier and more convenient, we need to be mindful of its potential negative consequences and work to mitigate them.2. How do you think technology will continue to evolve in the future?I believe that technology will continue to evolve at an exponential rate in the future. We will see advancements in artificial intelligence, virtual and augmented reality, and the Internet of Things. These technologies will transformthe way we live, work, and interact with each other. However, we must also be aware of the ethical implications of these technologies and ensure that they are developed and used responsibly.3. What are some of the benefits and drawbacks ofsocial media?Social media has revolutionized the way we communicate and connect with others. It has allowed us to stay in touch with friends and family, share information and ideas, and build communities around common interests. However, it has also led to addiction, cyberbullying, and the spread of fake news and misinformation. While social media has its benefits, we need to be aware of its potential pitfalls and use it responsibly.4. How has technology changed the way we work?Technology has transformed the way we work by making it more flexible and remote. With the rise of telecommuting and remote work, people can now work from anywhere in theworld as long as they have an internet connection. This has led to increased productivity, reduced commuting time and costs, and improved work-life balance. However, it has also led to a blurring of the boundaries between work and personal life, and the need for employers to ensure that remote workers are not isolated or overworked.5. What are some of the potential risks of artificial intelligence?Artificial intelligence has the potential to revolutionize many industries, from healthcare to financeto transportation. However, it also poses significant risks, such as the displacement of jobs, the concentration ofpower in the hands of a few tech companies, and thepotential for bias and discrimination in decision-making. We need to ensure that AI is developed and used in a waythat is transparent, fair, and accountable, and that it benefits society as a whole.。

如何快速有效阅读英文文献阅读英文文献是学术研究和知识获取的重要部分。

随着信息量的增加和时间有限，快速有效地阅读变得尤为重要。

以下是一些方法和技巧，可以帮助你快速有效阅读英文文献。

1.阅读前的准备工作在开始阅读之前，做一些准备工作可以帮助你更好地理解文献内容。

首先，浏览文献摘要，了解研究目的、方法和结论。

其次，查阅相关的定义、术语和背景知识，以确保你能够理解文章中的专业术语和概念。

2.浏览文章结构在开始详细阅读之前，先浏览一遍文章的结构，包括引言、方法、结果和讨论等部分。

这样可以帮助你获得对整篇文章的整体了解，并更好地理解每个部分的内容和主题。

3.利用标题和副标题标题和副标题通常是对文章内容的概括和总结。

阅读这些标题和副标题可以帮助你快速了解文章的结构和主要观点。

5.精读核心段落6.阅读图表和图片图表和图片通常是对研究数据和结果的可视化呈现。

阅读图表和图片可以帮助你更好地理解研究结果。

同时，注意图表和图片的标题和图例，以获取更多的信息。

8.做好笔记在阅读过程中，做好笔记是非常重要的。

可以使用高亮标记、便条贴或笔记本来记录重点观点、关键词和其他相关信息。

这样可以帮助你更好地理解和记忆文献内容，并在需要时方便查阅。

9.制定阅读计划制定一个阅读计划可以帮助你高效地阅读文献。

可以根据自己的时间和能力，设置每天或每周的阅读目标。

并使用特定的时间段来专注于阅读，避免分散注意力和拖延阅读。

10.练习速读技巧速读是一种通过提高阅读速度和理解能力来快速阅读大量文献的技巧。

可以通过使用手指或铅笔来引导阅读速度，提高目光移动的速度。

同时，练习识别文章的关键词、主题句和段落大意等技巧，可以帮助你更快地理解文章内容。

总之，快速有效地阅读英文文献是一项需要技巧和经验的任务。

通过以上的方法和技巧，你可以更好地理解和利用英文文献，提高学术研究和知识获取的效率。

科技文献中英文摘要范文English:Nowadays, with the rapid advancement of technology, there has been increasing interest in applying artificial intelligence (AI) to various fields such as healthcare, finance, transportation, and more. AI has the potential to revolutionize these industries by improving efficiency, accuracy, and decision-making processes. In healthcare, AI tools can assist doctors in diagnosing diseases, predicting patient outcomes, and even personalizing treatment plans. In finance, AI algorithms can analyze market trends, predict stock prices, and detect fraudulent activities. In transportation, AI can optimize routes, reduce traffic congestion, and improve safety measures. Despite the great benefits AI can bring, there are also ethical and privacy concerns that need to be addressed. It is essential for policymakers, researchers, and industry professionals to work together to ensure responsible and ethical AI development.中文翻译:如今，随着科技的快速发展，人们越来越热衷于将人工智能（AI）应用于医疗保健、金融、交通等各个领域。

面对海量的文献信息我们往往会感觉无从下手，更不要提阅读外国文献了。

但是阅读外国文献对于把握最新科研动态，扩充自己的知识是非常有必要的，今天我们一起来看看牛人们是怎样阅读外国文献的~~学术牛人1：用自己的话概括和梳理文献及时回顾心得和经验：我现在每天还保持读至少2-3 篇的文献的习惯.读文献有不同的读法.但最重要的自己总结概括这篇文献到底说了什么,否则就是白读,读的时候好像什么都明白,一合上就什么都不知道,这是读文献的大忌,既浪费时间,最重要的是,没有养成良好的习惯,导致以后不愿意读文献.1.回顾重要内容每次读完文献 (不管是细读还是粗读), 合上文献后,想想看,文章最重要的 take home message 是什么, 如果不知道,就从abstract,conclusion 里找, 并且从discuss 里最好确认一下. 这样一来, 一篇文章就过关了. take home message 其实都不会很多, 基本上是一些concepts,如果你发现你需要记得很多,那往往是没有读到重点.2.扩充知识面的读法重点读introduction, 看人家提出的问题,以及目前的进展类似的文章, 每天读一两篇,一个月内就基本上对这个领域的某个方向有个大概的了解.读好的review也行, 但这样人容易懒惰.3.为了写文章的读法读文章的时候, 尤其是看discussion 的时候,看到好的英文句型, 最好有意识的记一下,看一下作者是谁,哪篇文章,哪个期刊, 这样以后照猫画虎写的时候,效率高些.比自己在那里半天琢磨出一个句子强的多. 当然,读的多,写的多,你需要记得句型就越少.其实很简单,有意识的去总结和记亿, 就不容易忘记.学术牛人2：根据文献重要程度编号精读综述和摘要一、先看综述先读综述,可以更好地认识课题,知道已经做出什么，自己要做什么,,还有什么问题没有解决。

对于国内文献一般批评的声音很多.但它是你迅速了解你的研究领域的入口,在此之后,你再看外文文献会比一开始直接看外文文献理解的快得多。

阅读英語科技文章的技能和技巧简述当代科学技术发展迅速，每天有大量的英语科技文章、新闻及其它科技资料发表在各类报刊和网络上，要想把这些英语科技文献资料都及时翻译成中文是不可能的。

如果想要及时掌握最新的科技信息，把握住现代科技发展的脉搏，最好的解决办法是自己直接阅读英语文献资料，获得第一手信息。

只要有较好英语的基础，再掌握英语阅读的技巧，做到这一点并非很难。

阅读技能是学习任何语言的基本技能之一。

语言技能有四种，即听、说、读和写，其中说和写的技能属于主动性技能，比较难掌握，而听和读的技能属于被动性技能，比较容易掌握。

阅读技能相对来讲是最容易掌握的技能。

为什么阅读技能会比较容易掌握，因为人们在阅读时，可以自己控制阅读速度，可以查阅字典，压力较少，因此比较容易达到人们的阅读目的。

本文将以一些阅读实例，来讨论英语阅读技能和技巧，及其掌握学习的方法。

英语语言教学和研究人员对英语阅读技能和技巧的分类有所不同，但基本上可分为四种。

第一种是精读(intensive reading skill)；第二种是泛读(extensive reading skill)；第三种是略读(skimming reading skill)；第四种是掠读(scanning reading skill)；每种阅读技能和技巧都有其特点和要求，下面分别对这四种阅读技能和技巧做一些介绍。

精读技能精读(Intensive Reading)在四种阅读技能和技巧中要求最高，对所阅读的文章，要做到逐字细读，不但要了解文章的主题思想和内容，了解文章的文法结构，而且要掌握每个字词的意义和用法，必要时还需要把文章翻译成中文。

精读阅读技能是学习和研究英语的人或从事翻译人员必需要掌握的技能，但对只需要查阅英语科技文献和信息的科技工作者，在多数情况下不需要使用精读技能。

运用精读技能，不是看文章的长短，而在于是否需要对所阅读的英语资料文章做深度了解和研究。

下面以一则英语新闻为例，来简要说明通过精读，要到达什么样的标准？英语原文：(此文摘自2000年3月25日美国加利福尼亚州硅谷地区一份非常具有权威性的，以科技消息为主的报纸《圣荷西水星报(San Jose Mercury News)》商业版C1科技新闻部分)IBM Developing chips for TV set-top boxes Computer giant IBM said Friday it isdeveloping chips for televison set-top boxes that will transform TV sets intointeractive, two-way information appliances. By Computing PowerPC processorsand television set-top box components into a single "system-on-a-chip," theArmonk, N.Y., company aims toimprove system performance and lower prices."The PowerPc is an ideal chip because it has a good radio of power consumption, performance and low cost,”said Tom Haffhil, an analyst forMicroDesign Resource.分析：本文是一则新闻，报导美国IBM公司研发新产品的消息，其标题是IBM Developingchips for TV set-top boxes，意为“IBM公司研发电视机顶盒芯片”这篇短文共有81个字，三个句子，二个复合句，其中有一个是直接引语，还有一简单句。

英语科技文献阅读
英语科技文献阅读是获取科技信息、了解科技前沿的重要途径。

以下是一些建议，帮助你提高英语科技文献阅读能力：
1.掌握科技英语基础知识：包括科技英语词汇、语法和表达方式等。

可以通过学习专业词典、科技英语语法书籍等来加深对科技英语的理解。

2.拓展学科知识：科技文献往往涉及多个学科领域，因此具备广泛的知识背景是提高阅读效率的基础。

可以尝试涉猎不同领域的科技文献，了解不同领域的最新进展和趋势。

3.注重阅读技巧：掌握一些阅读技巧，如快速浏览、筛选信息、归纳总结等，可以提高阅读效率和质量。

同时，要注意避免逐字逐句翻译，而是要学会抓住文章的主旨和重点。

4.练习翻译和写作：对于非英语母语的读者，翻译和写作是提高科技文献阅读能力的关键。

可以通过练习将英文文献翻译成中文，或者将自己的研究成果写成英文论文来提高英语水平和表达能力。

5.利用辅助工具：可以使用一些辅助工具，如在线词典、翻译软件等，帮助理解生词和长难句。

同时，也可以利用学术搜索引擎、学术数据库等资源，查找和获取更多的科技文献资源。

6.参加学术交流活动：参加学术会议、研讨会等学术交流活动，可以了解最新的学术进展和动态，同时也可以与同行交流学习心得和经验，提高自己的学术水平和英语科技文献阅读能力。

总之，英语科技文献阅读需要不断积累和实践。

通过掌握基础知识、拓展学科知识、注重阅读技巧、练习翻译和写作、利用辅助工具以及参加学术交流活动等方法，可以逐步提高自己的英语科技文献阅读能力，更好地了解科技前沿和发展趋势。

阅读英文文献的技巧
阅读英文文献是学术研究中不可或缺的一部分,以下是一些技巧可以帮助读者更有效地阅读英文文献:
1. 熟悉学术写作格式:英文文献通常采用特定的学术写作格式,如APA、MLA、Chicago等。

在阅读前,先了解这些格式并熟悉它们,这将有助于读者更好地理解文献中的内容。

2. 阅读文献前先搜索:在阅读英文文献之前,先通过学术搜索引擎(如Google Scholar、PubMed等)进行文献搜索,这将有助于读者找到相关的文献,并避免阅读一些不相关的内容。

3. 摘要和关键词阅读:文献的摘要和关键词是读者快速了解文献的主要内
容和贡献的关键信息。

读者应该仔细阅读摘要和关键词,以确定文献是否与自己的研究方向相关。

4. 阅读多个文献:在研究过程中,可能会需要阅读多个文献,每个文献都有
不同的观点和贡献。

因此,读者应该尝试阅读多个文献,以更全面地了解研究领域。

5. 笔记和注释:在阅读文献时,可以使用笔记和注释来记录重要的信息,如
作者、文献来源、时间、主题等。

这将有助于读者更好地理解文献内容,并在以后阅读时进行回顾。

6. 寻求帮助:如果读者在阅读英文文献时遇到困难,可以向导师、同事或其他学者寻求帮助。

他们可以提供有用的建议和指导,帮助读者更好地理解文献内容。

以上是一些阅读英文文献的技巧,读者可以根据自己的研究需要和实际情况选择合适的技巧。

The quartz crystal model and its frequencies1. IntroductionThe region between F 1 and F 2 is a region of positive reactance, and hence is called the inductive region. For a given AC voltage across the crystal, the net current flow through the crystal is greatest at F 1 and least at F 2. In loose terms, F 1 is referred to as the series-resonant frequency and F 2 is referred to as the parallel-resonant frequency (also called antiresonance).In this note, we present some of the basic electrical properties of quartz crystals. In particular, we present the 4-parameter crystal model, examine its resonant and antiresonant frequencies, and determine the frequency at load capacitance. Our coverage is brief, yet complete enough to cover most cases of practical interest. For further information, the interested reader should consult References [1] and [2]. The model and analysis is applicable to most types of quartz crystals, in particular tuning-fork, extensional-mode, and AT-cut resonators.Likewise, we can express the impedance in terms of its resistance (real part) and reactance (imaginary part) as shown in Figure 2.1.1 OverviewTo begin, let’s look at the impedance of a real 20 MHz crystal around its fundamental mode.Figure 2—Impedance resistance R (log scale) and reactance X versus frequency for the same crystal shown in Figure 1.Frequency [Hz]R e a c t a n c e X [o h m s ]Figure 1—Impedance magnitude |Z| (log scale) and phase θ versus frequency for an approximately 20 MHz crystal. (Scans made with an Agilent 4294A Impedance Analyzer.)In this impedance scan over frequency (Figure 1), we see the following qualitative behavior. There are twofrequencies F 1 and F 2 where the phaseθ is zero. Below and away from F 1, the phase is approximately -90°. Near F 1 the phase makes a fast transition from -90° to +90°. Between F 1 and F 2 the phase remains approximately constant at +90°. Near F 2 the phase makes a fast transition from +90° to -90°. Lastly, above and away from F 2, the phase is again approximately -90°. Further, the impedance of the crystal is least at F 1 and greatest at F 2.Figure 3—Close-up of reactance X near F 1. The reactance iszero at a frequency slightly above 20 MHz.The resistance R is strongly peaked at the frequency F 2. Below F 1, the reactance is negative and increases to zero at F 1 (see Figure 3) and then increases to large positive values as F 2 is approached. At F 2, the1.2.3Frequency at load capacitancereactance quickly decreases to large negative values and then again steadily increases towards zero.Another important crystal frequency is the frequency F L at a load capacitance C L . (See Reference [3] for a full discussion of this concept.) At this frequency, the crystal reactance X is equal to 1.2The crystal frequencies1.2.1The series-resonant frequenciesConsider the frequency F 1. One can define this in at least three ways. One choice is the (lower) frequency F r where the phase of the crystal is zero. At this zero-phase frequency, the crystal is purely resistive (equivalently its reactance is zero). A second choice is the frequency F m of minimum impedance. A third choice is to define this as the series-resonant frequency F s —a frequency whose definition requires the crystal model as discussed in Section 2.LC X ω1=, (4) where ω = 2πF L . Equivalently, at this frequency, the series combination of the crystal and a capacitance C L has zero reactance. (See Figure 4.) Note that as C L → ∞, F L → F r , and that as C L decreases, F L increases towards F p .Table 3—Frequency at load capacitanceTable 1—The series-resonant frequenciesFrequency Description L FrequencyDescriptionF s Series resonant frequency F r Zero-phase frequency (lower) F m Minimum impedance frequencyIt turns out that for most crystals, F s , F r , and F m areall sufficiently close to one another than it is notnecessary to distinguish between them.. (1)m r s F F F ≈≈The resulting relation giving the frequency of a crystal as a function of its parameters and a load capacitance C L is called the crystal-frequency equation and is of prime importance in specifying and understanding the operation of crystals in oscillators. (See References [3] and [4].)CrystalC LSee Section 6.2 for further details. 1.2.2The parallel-resonant frequenciesNext consider the frequency F 2. One can also definethis in at least three ways. One choice is the (upper) frequency F a where the phase of the crystal is zero. At this zero-phase frequency, the crystal is purely resistive (being very high). A second choice is the frequency F n of maximum impedance. A third choice is to define this as the parallel-resonant frequency F p —a frequency whose definition also requires the crystal model as discussed in Section 2.Figure 4—Defining F L at C LAs we shall see, for most applications, the frequency F L at load capacitance C L is well approximated by the expression()++≈L s L C C C F F 0121. (5)1.3 Guide to this noteTable 2—The parallel-resonant frequenciesFrequency Description F p Parallel-resonant frequency F a Zero-phase frequency (upper)F nMaximum-impedance frequency For most crystals, F p , F a , and F n are all sufficiently close to one another than it is not necessary to distinguish between them. . (2)n a p F F F ≈≈Further, they are above F s and are normally wellapproximated by the expression+≈0121C C F F s p . (3) In Section 2, we present and discuss the 4-parametercrystal model. In Section 3, we derive some simple results from this model defining F s and F p . In Section 4, we define the three non-dimensionalquantities r , Q , and M . In Section 5, we present some useful properties of the frequencies F r , F a , F s , and F p . In Section 6, we present approximations for F L and F rthat go beyond the approximations in Section 1.2. In Section 7, we derive the exact expressions for F L and F r . In Section 8, we make a few comments on resistance at resonance and antiresonance. Lastly, Appendix 1 contains a list of the important symbols used in this note. Note that while we present both exact and approximate relations for F s , F r , F p , F a , and F L , we present no further results for F m or F n other than theapproximations given in Section 1.2. For further information, see References [5], [6], and [7].For those first becoming acquainted with crystals, we recommend reading Sections 1-4. For those who want further details and more precise results, we recommend reading Sections 1-6. Lastly, for those who want exact results, we recommend this entire note.Throughout, we use the usual relation between a given frequency f and its angular frequency ω counterpartf π2=ω. (6)2. The 4-parameter crystal modelThe modes of interest in quartz crystals are usuallymodeled electrically by the 4-parameter model shown in Figure 5. This model consists of two arms in parallel with one another. The “static arm” consists of a single capacitance C 0 (also referred to as the shunt capacitance). Herein, this capacitance includes the capacitance of the bare crystal and the shunt capacitance of its packaging. The “motional arm” consists of the series combination of a resistance R 1, inductance L 1, and a capacitance C 1.111C 0Figure 5—The 4-parameter crystal modelWhile this model is an approximation of the electricalcharacteristics of the crystal, it is a very good one and for most purposes more than sufficient. So, from here on, we take this model seriously. (See References [1] and [8] for further discussion.) One should be aware that crystals are complicated by the existence of many modes of oscillation. In addition to their fundamental mode, crystals have overtone modes. For example, tuning-fork crystals have 1st -overtone modes at roughly six times the frequency of the fundamental mode. As another example, AT-cut crystals have 3rd , 5th , 7th , etc., overtone modes with frequencies being nearly the overtone number times the fundamental mode frequency. Sometimes these modes are the desired mode as they can offer frequencies that would otherwise be unattainable.1 When they are not the desired mode, their great separation from the main mode and their resistance is normally sufficiently high that they have no effect on the performance of the crystal in an oscillator. AT-cut crystals are further complicated by the existence of anharmonic modes just above the main mode as well as having other unwanted modes. Proper crystal design minimizes the strengths of these modes (collectively referred to as unwanted modes) so that they have no effect on the crystal’s operation in an oscillator.2.1 Typical valuesTo give the reader some idea of these crystal parameters and how they vary with crystal type and frequency, we present some typical values for Statek crystals. However, keep in mind that ranges given here can be exceeded in some cases.The static capacitance C 0 has a limited range of variation, usually being on the order of 1-3 pF. This parameter typically scales with the motional capacitance C 1 and package size, i.e. crystals with large C 1 in large packages have large C 0. Smaller crystals also tend to have smaller C 1, so C 0 roughly correlates with package size, but not absolutely. Similarly, the motional capacitance C 1 has a fairly limited range typically being on the order of 0.5 fF to 10 fF. Tuning-fork and extensional-mode crystals tend to have their C 1 lie on the low end of this spectrum, while AT-cut crystals can have a C 1 just about anywhere in this range, depending on the size of the crystal and its frequency.The motional inductance L 1 varies greatly over frequency, for as we shall see, it is determined by C 1 and the crystal frequency. It has a high of roughly 100 kH for 10 kHz crystals to a low of less than 1 mH for 100 MHz crystals (a range of about 108 ). Lastly, the crystal resistance also varies greatly over frequency from a high of about 1 M Ω for 10 kHz H-type crystals to a low of about 10 Ω for high-frequency AT-cut crystals (a range of about 105 ).2.2 Specifying crystal parametersIf your application has critical requirements that require specification of the crystal parameters, then bounds on the relevant parameters should be supplied. However, unnecessary requirements will probably increase the cost of the crystal without any added benefit.The crystal parameter that most commonly requires specification is the crystal resistance R 1. This parameter plays an important role in the crystal-oscillator gain requirement and sometimes an upper1It is normally a mistake to use a crystal designed for fundamental mode operation at one of its overtone modes.3.1 Series resonancebound on R 1 is required to ensure the startup of the oscillator.Being a capacitance, the reactance of the static arm is negative. On the other hand, the motional arm consisting of the series combination an inductor and a capacitor can have reactance of either sign depending on the frequency. In particular at some frequency F s , called the series-resonant frequency, For applications requiring crystal pullability (the ability to change frequency with changes in load capacitance), bounds should be placed on C 1. As shown by Equation (5), C 1 plays a primary role in determining the frequency change for a given change in C L . The capacitance C 0 also plays a role and when the pullability requirements are demanding, upper bounds are placed on C 0.0. (12)1=X Using Equation (11), we see that the angular frequency ωs at which the reactance of the motional arm is zero is given by Lastly, requirements on L 1 are rarely necessary as such conditions can be expressed as conditions on C 1. [See Equation (14).]111C L s =ω. (13)Sometimes people place requirements on the crystal Q (defined below) in the belief that this quantity determines either oscillator startup or crystal pullability. Both are wrong. The resistance R 1 (along with the oscillator design) determines startup. The motional capacitance C 1 (along with C 0) determines the crystal pullability. [See Equation (5).]Therefore, the series-resonant frequency of the crystal is given by111π21C L F s =. (14)3. Simple consequencesEquivalently, ignoring the crystal resistance R 1, series resonance is the frequency at which the crystal impedance is minimal (being zero in this idealization).In this section we derive some simple consequences of the crystal model. In particular, we show the existence of a series-resonant frequency F s and a parallel-resonant frequency F p .The impedance Z of the crystal is determined by the parallel combination of the impedance Z 0 of the static arm and the impedance Z 1 of the motional arm. 1010Z Z ZZ Z +=. (7)Note that one should not use Equation (14) to compute F s as typically neither L 1 and C 1 are knownonly to about 1% accuracy while other methods can determine F s to better than 1 ppm. Instead, the utility of Equation (14) comes in computing either L 1 or C 1from the other and F s . 3.2 Parallel resonance The impedance of the static arm is purely reactive and is given by, (8)00jX Z =where its reactance X 0 is given by01C X ω−=. (9) One effect of the static (shunt) capacitance C 0 is to make the crystal look like a simple capacitance at frequencies where the impedance of the motional armis large compared to impedance of the static arm. Another is to create an anti-resonance (resonance of high impedance) at a frequency where the two armsof the crystal resonant in which such a way to offerhigh impedance to current flow. Likewise, the impedance of the motional arm is given by111jX R Z +=, (10)Ignoring the crystal resistance R 1, this parallel resonance occurs at the frequency where the admittance Y = 1/Z of the crystal is zero.where its reactance X 1 is given by1111C L X ωω−=. (11) .1101010jX jX Y Y Y+=+== (15) Therefore010=+X X , (16)or equivalently11C X ω=. (17)()++≈L s L C C C F F 0121.(23)With this, it follows that the parallel-resonantfrequency F p of the crystal is given by11C CF F s p +=. (18)This is the standard crystal-frequency equation. However, be aware that it is an approximation. Even so, in most cases this equation is sufficient and a more exact expression would complicate the computation without any benefit. 3.4 The significance of L 1Note that the parallel resonant frequency is alwaysabove the series-resonant frequency and that their separation is determined by the ratio of the capacitances C 1 and C 0. For quartz crystals, C 1 << C 0, so F s and F p are quite close is as fraction of absolute frequency and is usually well approximated by the expression Note that+≈0121C C F F s p . (19),at 4122112111s F f L C L d dX df dX ==+==πωπωπ (24)which shows that L 1 is proportional to the rate of change of the motional reactance with frequency atseries resonance. This fact is sometimes useful in measuring the crystal parameters. Note that, ignoring the effects of resistance, dX/df = 4πL 1 at f = F s , showing that the shunt capacitance C 0 does not modify the slope of reactance curve at series resonance. However, the shunt capacitance does greatly increase the slope of the reactance asantiresonance is approached. (See Figure 2 andFigure 3.) While the motivation for our definition of the parallel-resonant frequency was based on the case where the crystal resistance is zero, we take its definition in general to be that frequency where the reactances of the two arms are in anti-resonance. Therefore, the parallel resonant frequency F p of a crystal is always given by Equation (18). 3.3 F L at C L Ignoring the crystal resistance R 1, we can easily work out the crystal frequency F L at a load capacitance C L . This is frequency at which4. Three non-dimensional quantities There are at least three non-dimensional quantities that are very useful in characterizing crystals.()(),11111010jX C j C j Y Y ZL +−=+=ωω (20) Our first quantity is the capacitance ratio r10C Cr =. (25) and so()L C C X +=011ω. (21)As we saw in Section 3.2, 1/r determines theseparation between series resonance and parallelresonance, in other words, the width of the crystal’s inductive region. As an example, a crystal with a C 0of 2 pF and a C 1 of 5 fF has a capacitance ratio of 400. For Statek crystals, r can range from about 250to 1,000.2With this is it straightforward to show that the frequency F L at load capacitance C L is given by )0( ,1101=++=R C C C F F Ls L . (22) Our next quantity is the crystal quality factor Q . Thisis defined so that 2π/Q is the fractional energy lost per cycle in the crystal and is given in terms of the crystal parameters by Although this derivation ignores the crystalresistance, our final expression is sufficient for mostapplications and in fact is normally further approximated by the expression2These bounds can be exceeded.111C R Q s ω=. (26) 6. Approximations beyond R 1 = 0 For the zero-phase frequency F r , the frequency F L at load capacitance C L , and crystal resistance at loadcapacitance, we simply present approximateexpressions that go beyond the results presented sofar. For proof, see the exact results in Section 7.where the frequency ωs (angular series resonance) isgiven by Equation (13). Crystals with large Qoscillate many cycles before their oscillations decayappreciably. For Statek crystals, Q ranges from about 2,000 to 400,000.2 6.1 Approximating F Lat C LA direct consequence of its definition is that it takesπ2Q(27) In cases where further accuracy is required in theload frequency F L , then to second order in resistance++ ++≈L L s L C C QM C C C F F 0011111. (32) cycles for the oscillation energy an isolated crystal to ramp-down by a factor of 1/e . The number of cycles for ramp-up is the same. So, the time for oscillationsto ramp-up or ramp-down in a low-frequency high-Qcrystal can be quite long—on the order of seconds. 6.2 Approximating F r Normally, F r is well approximated by F s . To see thedifference between the two, we must look to second order in crystal resistance. To this order, F r is slightly above F s by the amount Our last quantity is the crystal figure-of-merit M .This is simply the ratio of the impedance of the staticarm to the impedance of the motional arm at series resonance. Given this, it is straightforward to showthat M is given by11C R M s ω=. (28)+≈QMF F s r 211. (33)This result can be obtained from Equation (32) by taking the limit C L → ∞ and performing a first-order expansion in 1/(QM ). As we shall show in Section 7.3, in order for thecrystal to posses an inductive region, M be greaterthan 2. For Statek crystals, M ranges from about 10to 300.2Note our three parameters are not independent;indeed. (29) Mr Q =In most cases, QM > 106 so that ignoring the effect ofresistance is to make an error below 1 part-per-million in frequency, which is usually acceptable. An interesting exception is the case of 10 kHz H-type crystals. The large resistance (about 1 M Ω) of thesecrystals give Q ≈ 4,000 and a figure-of-merit M ≈ 11 and so that the difference between F r and F s is about 11 ppm.5. Some useful frequency properties6.3 Approximating R at F L5.1The frequency product propertyIt turns out, without approximation, that . (30)p s a r F F F F =The crystal resistance R depends on the frequency ofinterest. At series resonance, R ≈ R 1 and it increasesto very large values near parallel resonance. (SeeFigure 2.) A natural question that comes up is what is the crystal resistance at the load frequency F L . It turns out to good approximation that This equality allows us to calculate any one of theabove four frequencies given the other three.Because of this and the fact that results beyond theapproximation F a ≈ F p are rarely required, we do not present any further expressions for F a .211+≈L CC R R . (34) So, as expected, the crystal resistance is approximately R 1 at F r and increases to very large values as C L approaches zero.5.2 The frequency inequalitiesWhen the crystal posses an inductive region (so F r and F a exist and are distinct), (31)p a r s F F F F ≤<≤with equalities when and only when R 1 = 0.7. Exact expressionsand10X X X +=Ω. (42) 7.1 Crystal impedanceWe express the crystal impedance Z in terms of the impedances of the two parallel arms as follows.2102102011010Z Z Z Z Z Z Z Z Z Z Z ++=+=(35)With these definitions, we can express the crystal resistance R as()()+−+=−221/111M r R R , (43)and the reactance as()()220/111+−+Ω−=−M r X X . (44) Denoting resistance of the crystal by R (R = Re(Z ))and its reactance by X (X = Im(Z )), so that 7.3 F L at C L (exact),jX R Z +=Using Equation (44) and the fact that X = 1/(ωC L ), we havethen Equations (8) and (10), give the following expression for the crystal resistance R()()220/111+−+Ω−=−−M r C C L , (45)++=1021201X X R X R R , (36) which gives us the following quadratic equationfor Ωand the following for the crystal reactance X()().110211000210212101210+++−=++++=X X R X X X X X X R X X X R X X (37) 0111111202= ++Ω ++−Ωr M QM C C L . (46) It can be shown that the existence of real frequencies requires that+ +++>L L C C Q C C C M 0011112. (47)It can be shown that Z (ω) sweeps out an approximatecircle in the impedance plane (and similarly Y (ω) sweeps out an approximate circle in the admittance plane). See References [5], [6], and [7] for further details.Alternatively, for a given crystal, there is a lower bound on the allowed load capacitance C L , i.e. arbitrarily small load capacitances are not allowed. However, this bound is usually so weak that it causes no practical limitation to the existence of F L . 7.2 NormalizationDefine the normalized “frequency” Ω by22sp s ωωωω−−=Ω. (38) Taking the limit C L → ∞, we see that the conditionfor the existence of an inductive region is thatQM 12+>, (48) Note that Ω = 0 at F s and Ω = 1 at F p . In terms of Ω, the (angular) frequency isr sΩ+=1ωω. (39)showing that M must be greater than 2.Define the quantity ξ byFurther set Ω−=Ω1. (40)QMC C L 1110−+=ξ. (49)Note that1X X −=Ω, (41)Note that ξ > 0 by Equation (47). Further, define the quantity χ by9. References++−+=L CC C M 0122142ξξχ. (50)1. Bottom, Virgil E., Introduction to Quartz CrystalUnit Design , Van Nostrand Reinhold Company, 1982. With these definitions, solving Equation (46) and using Equation (39), the frequency F L at load capacitance C L is given by 2. Parzen, Benjamin , Design of Crystal and OtherHarmonic Oscillators , UMI Books on Demand, 1999.+++=QM CC C F F L s L χ1101. (51) 3. Statek Technical Note 33. 4. Statek Technical Note 30.5. EIA Standard EIA-512, 1985, Standard Methodsfor Measurement of Equivalent Electrical Parameters of Quartz Crystal Units, 1 kHz to 1 GHz . Note that actually there is a second root of Equation (46). However, the frequency corresponding to this root corresponds to a frequency very near anti-resonance where the resistance is very high; this is not the frequency of interest.6. IEEE Standard 177, 1966, Standard Definitionsand Methods of Measurements for Piezoelectric Vibrators . 7.4 F r (exact)Taking the limit C L → ∞ in the above equation for F L gives F r (the lower frequency at which the reactance of the crystal is zero) 7. Hafner, Erich, The Piezoelectric Crystal Unit—Definitions and Methods of Measurement , Proceedings of the IEEE, Volume 57, No. 2, 1966.− −+−+=2241111211M QM QMQM F s r F (52)8. Cady, Walter Guyton, Piezoelectricity , McGraw-Hill Book Company, Inc., 1946.8. Final comments on crystal resistanceNote that the crystal’s resistance at neither F s nor F ris R 1. Instead, 1211)(R M R F R s <+=−, (53)and1211)(R M R F R r >−≈−. (54)However, normally such distinctions are not required as they differ from R 1 by much less than 1%. Lastly, near antiresonance,, (55)21)(M R F R p ≈showing that 2M is roughly the range of the crystal resistance over frequency. (In fact, 2M is also roughly the range of the crystal impedance over frequency.)10. Appendix 1—Table of symbolsTable 4—Symbols used to describe crystalsSymbol Alternates Descriptionf FrequencyωAngular frequency, ω = 2π fC0Static (shunt) capacitanceR1R m, R1, RR3Motional resistanceL1L m, L1Motional inductanceC1C m, C1Motional capacitancer Capacitance ratio, r = C0/C1Resonator quality factor, Q = 1/(ωs R1C1)Figure of merit, M = 1/(ωs R1C1) = Q/rF s Series resonant frequencyF r FR Lower zero-phase frequency (normally close to F s)F m Minimum impedance frequency (normally close to F s)F p Parallel resonant frequencyF a Upper zero-phase frequency (normally close to F p)F n Maximum impedance frequency (normally close to F p)F L Frequency at load capacitance C LC L CL Load capacitanceTS Trim sensitivity, fractional rate-of-change of F L with C LCrystal impedance, Z = R+j X = |Z|eθR Crystal resistance, R = Re(Z)X Crystal reactance, X = Im(Z)θCrystal impedance phase angle, θ= arg(Z)3 Strictly speaking, RR (or Rr ) refers to the resistance at F r, however as shown in Section 8, the distinction between RR and R1 israrely worthwhile.。

（完整word版）英文科技文献阅读英文科技文献阅读英语阅读能力是一种重要的能力，养成良好的阅读习惯，掌握一定的阅读技巧，对于阅读能力的提高十分重要。

同学们要相信，良好的阅读习惯是可以培养的。

英语科技文献主要包括，专著（monograph/treatise）、教材(teaching material)、科研论文(research paper/thesis)、学位论文(dissertation)、科研报告(research report)、产品说明书(product operating instruction)、操作说明书(operation manual)、专利文献(patent document)、技术合同（technical contract）和广告(advertisement)等。

一般来说，英语科技文献的阅读方法与英语其他文献的阅读的方法相差不大。

我们先介绍几种阅读方法：采取何种阅读方法取决于阅读的目的。

略读（Skimming）：只需要理解文章内容的大约50%，快速地获取中心意思和重点。

速度为300~1000wpm（words per minute）。

关键是掌握英文的写作特点。

将重点放在句首和句尾的主题句上。

注意抓住关键词。

浏览或者查阅（Scanning）：查阅只需要从文章中有目的地迅速查找某一具体事实或者特定信息。

快速阅读（Fast reading）：速度为200~350 wpm。

要求基本上理解文章内容。

为了养成快速阅读的习惯，精读（Intensive reading）：在阅读的同时对文章从各方面（包括语法、词汇、写作特点和中心思想）进行分析。

阅读时要集中精力：阅读的过程过程如下：首先是利用眼睛从文献中获取文字、图形信息，然后大脑要对有关的信息进行记忆、理解并思考。

如果我们在阅读时还同时作其他的事情，比如说，听收音机、与他人聊天或考虑其他问题，势必会降低阅读的速度、影响对信息的记忆最终会影响对问题理解；这就好比一个计算机的CPU在同时执行多个任务时会降低速度一样。

科技文献英文摘要范文The rapid advancement of technology has reshaped ourdaily lives, making it easier to access information and communicate with others. This transformation has been drivenby innovations in artificial intelligence, big data, and the internet of things.In the field of healthcare, technology is revolutionizing patient care through telemedicine and the use of wearable devices that monitor vital signs in real-time. These advancements have the potential to improve outcomes andreduce healthcare costs.Environmental conservation is another area where technology plays a pivotal role. Renewable energy sources, such as solar and wind power, are becoming more efficient and affordable, reducing our reliance on fossil fuels andmitigating the impact of climate change.Education is also undergoing a digital transformation. Online learning platforms and virtual classrooms are making education more accessible and personalized, allowing students to learn at their own pace and from anywhere in the world.However, with these technological advancements come new challenges. Cybersecurity is a growing concern as more of our personal and professional lives move online. Ensuring the protection of data and privacy is crucial in this digital age.As we embrace the benefits of technology, it is important to consider the ethical implications of its use. The development of autonomous vehicles, for example, raises questions about safety, liability, and the potential impact on employment in the transportation sector.In conclusion, the integration of technology into various aspects of society offers immense opportunities for growth and improvement. Yet, it also necessitates a thoughtful approach to its implementation, ensuring that it serves the greater good and addresses the concerns that arise from its use.。

如何搜索查找外文英文文献及阅读指南搜索文献一定不要心浮气躁，要沉下心来。

在查找和阅读的过程中有的文献看懂了，但是看不懂的文献也可能会居多。

看懂的认真学习借鉴，看不懂的深入探索，实在不行就暂时放下，过一段时间，随着知识和能力的提高慢慢也就弄明白了一些。

即使还是看不懂，但是心里知道有那么回事，为将来的继续深造做了铺垫。

千万不要只是为看文献而看文献，我们看的目的是为了能为我们自己的科研所用，所以看的过程中一定要和你自己的数据相结合，当看完一篇文献后，要好好总结，如果用自己的数据，又该怎么样解释。

还有一些牛刊物上的文章，不但要学习文章里面的知识，还要学习牛人写文章的文风。

好的文章肯定会有好的文风，这些都是我们将来写文章要学习的。

一、如何进行文献检索英文文献检索首推Elsevier，Springer等。

虽然这些数据库里面文献已经不算少了。

但是有时还会碰到查不到的文献，而这些文献的数据库我们所在研究所或大学又没有买，怎么办？我基本通过以下向个途径来得到文献。

1、首先在Google学术搜索里进行搜索，里面一般会搜出来你要找的文献，在Google学术搜索里通常情况会出现“每组几个”等字样,然后进入后，分别点击，里面的其中一个就有可能会下到全文，当然这只是碰运气，不是万能的，因为我常常碰到这种情况，所以也算是得到全文文献的一条途径吧。

可以试一下。

同时，大家有没有发现，从Google学术搜索中，还可以得到一些信息，Google学术搜索中会显示出你搜索文章的引用次数，不过这个引用次数不准确，但是从侧面反应了这篇文章的质量,经典文章的引用次数绝对很高的。

同时如果你用作者进行搜索时，会按引用次数出现他写的全部的文章，就可以知道作者的哪些文章比较经典，在没有太多时间的情况下，就可以只看经典的。

2、如果上面的方法找不到全文，就把文章作者的名字或者文章的title 在Google里搜索（不是Google学术搜索），用作者的名字来搜索,是因为我发现很多国外作者都喜欢把文章的全文（PDF）直接挂在网上，一般情况下他们会把自己的文章挂在自己的个人主页（homepage）上，这样可能也是为了让别的研究者更加了解自己的学术领域，顺便推销自己吧。

如何阅读英文文献阅读英文文献是提高英语水平和专业知识的重要途径。

对于许多初次接触英文文献的人来说，仅仅依靠字典翻译，并不足以全面理解文献中的内容。

为了更好地阅读英文文献，下面将为你提供一些有用的技巧和建议。

1.熟悉文献结构：英文文献通常按照常规结构编写，包括摘要、引言、方法、结果和讨论部分。

在阅读之前，先熟悉这些部分的内容和顺序，这将帮助你更好地理解文献的组织结构和主要观点。

2.阅读摘要和标题：文献的摘要通常提供了对全文的概述和关键信息。

在开始全文阅读之前，先阅读摘要和标题，了解研究的目的、方法和主要结果，这有助于你确定是否继续阅读全文。

3.利用上下文推测词义：在阅读过程中，你可能会遇到一些生词和不熟悉的词汇。

此时，不要立即去查字典，尝试根据上下文推测其意思。

通过将其放入句子和段落的语境中，你可能能够理解其大致意思，从而更好地理解文献内容。

4.标记关键信息：在阅读过程中，使用标记或笔记来突出重要的观点、数据和引用。

这样做可以帮助你在之后翻阅时更快地找到相关信息，并帮助你更好地理解和消化文献。

5.阅读相关文献：阅读一篇文献时，经常会引用其他相关的文献。

如果你对该领域不够了解，不妨阅读这些相关文献，以加深对研究背景和领域知识的理解。

这有助于你更好地理解文献内涵，并从更广泛的角度看待问题。

8.注重语法和单词：在阅读文献的过程中，留意句子结构和语法使用。

如果遇到困难，可以参考语法书籍或向老师、同学寻求帮助。

同时，将常见的单词和短语列入生词表，并在之后的阅读中加以复习和应用。

9.常规阅读和扫描阅读结合：对于长篇文献或特定内容的深入阅读，可能需要花费较多时间。

然而，当你只是需要了解文献中的一些特定信息时，可以采用扫描阅读的方式快速获取所需信息。

在这种情况下，注重标题、摘要、图表和结论等部分的内容。

10.多读多练：在阅读英文文献上，没有捷径或替代品。

只通过不断的阅读才能提高阅读能力和理解能力。

因此，给自己设置阅读目标，并尽量多读不同领域的文献。

Technology Literature RetrievalCourse Code: 83158000Course Name: Technology Literature RetrievalCourse Credit: 1 Course Duration: Sixth SemesterTeaching Object: All Undergraduate Students in school of space science and physicsPre-course:General PhysicsCourse Director: Wang ShouYu Associate Professor Philosophical DoctorCourse Introduction:Technology Literature Retrieval is an elective course in the school of space science and physics. This course purpose makes the student to understand the basic principle and the method of the technology literature retrieval. In this course, students are asked to know different types of internet information databases, and master basic retrieval methods. The final goal is that the student can find itself to electronic periodicals, electronic books, and electronic papers in the later study or the work.Practical Activities:Students are required to carry out some practical operations on the Internet.Course Examination:Students’ Final Scores = Scores of Ordinary Tests * 30% + Scores of the Final Exam * 70% Scores of ordinary tests vary according to students’performance in attendance, homework and practical activities.The final exam will be an open-book exam.Appointed Teaching Materials:[1] Wang LiCheng. Technology Literature Retrieval. Nanjing: Southeast university Press，2006Bibliography:[1] Lai MaoSheng. Technology Literature Retrieval. Beijing: peking university Press，1994。

科技文献中英文摘要范文English:Scientific literature abstracts serve as concise summaries of research papers, providing readers with an overview of the study's purpose, methods, results, and conclusions. An effective abstract is typically structured into distinct sections, including background or context, objectives or aims, methods or approach, results or findings, and conclusions or implications. In the background section, the abstract introduces the topic of the study, highlighting its significance and relevance to the field. The objectives section outlines the specific goals or aims of the research, clarifying what the study aims to achieve or investigate. The methods section describes the methodologies employed in the study, including experimental procedures, data collection techniques, and analytical approaches. The results section presents the key findings or outcomes of the research, often including numerical data or statistical analyses. Finally, the conclusions section summarizes the main implications or significance of the study's findings, discussing their broader implications for the field or potential applications. Overall, a well-written abstract effectively communicates the essential aspects of theresearch paper, helping readers quickly grasp the study's key points and decide whether to read the full paper.中文翻译:科技文献摘要作为研究论文的简洁总结，为读者提供研究目的、方法、结果和结论的概述。

英文文献阅读方法1. 确定阅读目的在阅读英文文献之前，首先要明确阅读的目的。

是为了获取某方面的知识，还是为了查找支持自己观点的论据？不同的阅读目的会影响阅读的方式和深度。

2. 制定阅读计划在确定阅读目的的基础上，可以制定阅读计划。

考虑到时间和资源的限制，可以选择优先阅读具有代表性的文献，或者根据自己的研究方向和兴趣进行选择。

3. 阅读前的准备在开始阅读英文文献之前，可以先了解一些背景知识，比如作者的研究背景、研究方法和研究成果。

这样可以帮助我们更好地理解文献内容。

4. 速读在进行大量文献筛选时，可以采用速读的方式。

快速浏览文献的标题、摘要和关键词，以确定是否与自己的研究课题相关。

5. 详读对于与自己研究相关的文献，可以进行详细阅读。

可以逐段逐句地阅读，理解作者的论点、论据和结论，并思考其对自己研究的意义。

6. 笔记和摘录在阅读过程中，可以做好笔记和摘录工作。

可以记录下文献的主要观点、关键词和作者的论据，以备日后查阅。

7. 查找相关文献在阅读一篇文献的过程中，可能会涉及到其他相关的文献。

可以借助文献引用和检索工具，查找到相关的文献进行深入阅读。

8. 思考和总结阅读完毕后，可以对文献进行思考和总结。

可以思考文献的亮点和不足之处，以及对自己研究的启发和帮助。

9. 反复阅读有些重要的文献可能需要反复阅读。

通过多次阅读，可以更深入地理解文献内容，并为自己的研究提供更多的启发和支持。

10. 结合实际阅读完文献后，可以结合自己的研究实际，思考如何将文献中的观点和论据应用到自己的研究中，或者对文献中的研究方法和成果进行验证和拓展。

通过以上方法，可以更加有效地进行英文文献阅读，获取到有价值的知识和信息，为自己的研究工作提供支持和帮助。